1. Field of Invention
This invention relates generally to pouches or containers forming an envelope for protectively packaging food substances and other products, and more particularly to a pouch fabricated of laminate sheeting, at least one ply of which is an oriented synthetic plastic film which imparts high strength and tear resistance to the pouch.
2. Status of Prior Art
Pouches or containers for storing and dispensing flowable or solid food substances and other more or less perishable products are usually fabricated of a multi-ply laminate sheeting forming an envelope to protect the contents of the package and prolong its shelf life. The shelf life of a packaged product depends on the degree to which is isolated from the atmosphere in which the package is placed.
One well-known form of pouch serves to package a hot dog relish which is dispensed by tearing an opening in the pouch and then squeezing the pouch to extrude the relish therefrom. This pouch is formed of a laminate sheeting whose outer ply is a clear polyester film, the inner face of which is printed to identify the contents. The outer film ply is adhesively laminated to an intermediate ply of metal foil which in turn is adhesively laminated to an inner ply formed of polyethylene film.
The three plies which together create this laminate sheeting have distinctly different properties. The outer polyester film ply imparts strength and tear resistance to the pouch, the intermediate metal face ply acts as a moisture barrier, while the inner polyethylene ply facilitates sealing of the pouch.
The reason metal foil or a metallized plastic film is often included in laminate sheeting from which a pouch is fabricated to package food, is that plastic films, even those of exceptional tensile strength, have some degree of porosity. As a consequence, a pouch formed entirely of plastic film material will exhibit a moisture vapor transmission rate (MVTR) that is unsuitable in a food container. The transfer of moisture through the envelope of a food pouch reduces its shelf life, and a moisture barrier is therefore desireable.
A serious drawback of multi-ply laminate sheeting of the type heretofore used for fabricating pouches and other packaging material, does not entirely reside in the structure of the sheeting, but rather in the environmental conditions which prevail in the course of producing the sheeting.
Most industrial adhesives used to interlaminate the several plies of the laminate sheeting, include volatile chemical solvents which in the course of curing the adhesive are volatilized. The resultant noxious fumes which are driven off into the atmosphere are environmentally objectionable. It becomes necessary, therefore, in the plant in which the pouch laminate sheeting is produced, to provide filtration and other equipment to capture and treat the noxious fumes. This requirement adds substantially to the cost of production.
In those instances where hot melt adhesives are used to interlaminate the plies of the laminate sheeting, not only do some of these adhesives give off objectionable fumes, but the heat involved may have adverse effect on the plies to which the hot melt adhesive is applied. Thus if one of the plies is a synthetic plastic film that has been uni-axially or bi-axially oriented to enhance its tensile strength, this orientation will be impaired by heat, for heat acts to relax the film and in doing so, to destroy its orientation.
Of prior art background interest are the Fukushima U.S. Pat. No. 4,790,429, as well as the Redmond U.S. Pat. No. 3,986,640 and U.S. Pat. No. 4,724,982 which disclose various forms of pouches and containers for food products formed of plastic film material. The food pouch disclosed in the Sanni U.S. Pat. No. 3,366,229 uses a laminated sheeting of thermoplastic film and paper so that seal lines can be produced by thermal welding. The Martin U.S. Pat. No. 4,806,398 shows a carton for liquid formed by a paper substrate having bonded to one side a polyethylene film and to the other side a polyolefin film to provide a liquid-impermeable laminate that lends itself to thermal bonding. A similar container is shown in the Rawing U.S. Pat. No. 3,404,988.
In view of the foregoing, the main object of this invention is to provide a pouch or container forming an envelope for protectively packaging a food substance or other product, the pouch being fabricated of a laminate sheeting of exceptional strength.
A significant advantage of a laminate sheeting in accordance with the invention is that in the course of its production during which the plies of the sheeting are adhesively interlaminated no environmentally objectionable fumes are then emitted. It is therefore not necessary in a production plant to take measures to clean up the atmosphere.
More particularly, an object of this invention is to provide a laminate sheeting for fabricating pouches to package food substances or other products in which at least one ply of the sheeting is formed by an oriented synthetic plastic film of high strength whose orientation is unimpaired in the course of interlamination of the plies.
Briefly stated, these objects are attained by a pouch or other container forming an envelope for protectively packaging a product such as a flowable or solid food substance. The pouch is fabricated from a laminate sheeting whose plies have different properties that depend on package requirements, at least one ply in the laminate being an oriented, synthetic plastic film of high tensile strength. The plies are adhesively interlaminated at ambient temperature with a water-based adhesive whereby the orientation of the film is unaffected by the laminating process, in the course of which no environmentally objectionable fumes are discharged into the atmosphere.